1. Field of the Invention
The present invention relates to a loop brush roller as well as an image forming apparatus such as a copying machine, a printer, a facsimile machine or a combination machine thereof that has a loop brush roller and uses an electrophotographic method.
2. Description of the Related Art
A general image forming apparatus performs image formation, and has a cylindrical and rotatable image carrier, charging means for uniformly charging a surface of the image carrier, exposing means for exposing the image carrier to form an electrostatic latent image, developing means for developing the electrostatic latent image to form a toner image by a potential difference between a voltage applied to a developing unit and the electrostatic latent image, transferring and transporting means that is arranged to face a photosensitive drum for receiving a voltage opposite in polarity to the toner image, thereby transferring the toner image on the image carrier onto a transfer member such as a paper sheer and simultaneously transporting it, cleaning means that is in contact with the photosensitive drum for scraping untransferred residual toner that remains on the photosensitive drum without being transferred onto the transfer member, and fixing means for fixing the toner image onto the transfer member by applying heat and pressure to the toner image transferred onto the transfer member.
As the cleaning means, the apparatus uses a cleaning blade that scrapes the untransferred residual toner by pressing a strip of polyurethane against the image carrier.
In recent years, brush rollers have been used in various positions in the image forming apparatus. As the brush rollers, there have been a loop brush roller in which bundles of fibers extend through a base member formed by weaving warps and wefts together to form loop forms on one of the surfaces, as well as a straight-bristle brush roller having fiber bundles protruding from a base member.
Conventionally, the straight-bristle brush rollers having simple structures have been used in many cases, but use of the loop brush rollers is now spreading because the loop brush roller applies a lower pressure to a contact target and thus applies less damage thereto. A range of use thereof contains an electrically charging brush roller, a cleaning brush roller, a lubricant application brush roller, a paper dust removing brush roller and others. The case where it is used as the loop brush roller for applying the lubricant will be primarily described below.
When the loop brush roller is used, a manner of handling it must be different from that for the straight-bristle brush roller. For example, Japanese Laid-Open Patent Publication No. 2010-107683 (reference 1) has proposed a structure in which an angle formed by rotation directions of a loop brush roller and a brush roller is set in a predetermined fashion to reduce a frictional force between an end of a cleaning blade end and a surface of an image carrier member and thereby to allow a long-term use of the cleaning blade and the image carrier.
Further, Japanese Laid-Open Patent Publication No. 2010-097234 (reference 2) has made such a proposal that an angle of a line of intersection between a flat plane containing a loop and a base member surface is set to a predetermined angle, and thereby uniform scraping of solid lubricant as well as lubricant dropping by shaking it by flicker are achieved.
Japanese Laid-Open Patent Publication No. 06-289759 (reference 3) has disclosed a fur brush roller that is slidably in contact with a surface of an image carrier to clean the surface. This fur brush roller has looped fur members to be in contact with the surface of a latent image carrier, and the looped fur member has a space of at least 3 mm between opposite leg base ends of each member.
However, due to such a structure that the base member into which the loops are woven is spirally wound around a core roller, the loop brush roller suffers from a problem that the loops may fray when they receive a strong tensile force.
When fraying occurs in the loop brush roller that is used as the lubricant applying brush roller, the frayed fiber bundles are wound around the surface of the brush roller so that the leading end portion of the brush roller having a high lubricant-scraping ability is covered with the fiber bundles to lower its lubricant-scraping ability.
This reduces an amount of the lubricant that is supplied to the image carrier from the lubricant-supplying loop brush roller, and increases a friction that occurs between the cleaning blade and the image carrier, and the cleaning blade and the image carrier will become unusable due to wearing within a short term.